the enteropathogenic e. coli (epec) tir effector inhibits nf-κb activity by targeting tnfα receptor-associated factors致肠病的大肠杆菌(epec)行动效应抑制nf-κb活动针对tnfαreceptor-associated因素.pdf

The Enteropathogenic E. coli (EPEC) Tir Effector Inhibits NF-kB Activity by Targeting TNFa Receptor-Associated Factors ´ ` ¨ Marie-Helene Ruchaud-Sparagano, Sabrina Muhlen, Paul Dean, Brendan Kenny* Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Newcastle-upon-Tyne, United Kingdom Abstract Enteropathogenic Escherichia coli (EPEC) disease depends on the transfer of effector proteins into epithelia lining the human small intestine. EPEC E2348/69 has at least 20 effector genes of which six are located with the effector-delivery system genes on the Locus of Enterocyte Effacement (LEE) Pathogenicity Island. Our previous work implied that non-LEE-encoded (Nle) effectors possess functions that inhibit epithelial anti-microbial and inflammation-inducing responses by blocking NF-kB transcription factor activity. Indeed, screens by us and others have identified novel inhibitory mechanisms for NleC and NleH, with key co-operative functions for NleB1 and NleE1. Here, we demonstrate that the LEE-encoded Translocated- intimin receptor (Tir) effector has a potent and specific ability to inhibit NF-kB activation. Indeed, biochemical, imaging and immunoprecipitation studies reveal a novel inhibitory mechanism whereby Tir interaction with cytoplasm-located TNFa receptor-associated factor (TRAF) adaptor proteins induces their proteasomal-independent degradation. Infection studies support this Tir-TRAF relationship but reveal that Tir, like NleC and NleH, has a non-essential contribution in EPEC’s NF-kB inhibitory capacity linked to Tir’s activity being suppressed by undefined EPEC factors. Infections in a disease-relevant intestinal model confirm key NF-kB inhibitory roles for the NleB1/NleE1 effectors, with other studies providing